Tuesday, October 27, 2009

Drinking blood makes vampire spider sexier

In East Africa lives a species of spider that drinks mammalian blood. But fear not - Evarcha culicivora is an indirect vampire - it sates its thirst by preying on female mosquitoes that have previously fed on blood themselves.

Even though its habitat is full of non-biting midges called "lake flies", it can tell the difference between these insects and the blood-carrying mozzies it carries. Robert Jackson from the University of Canterbury discovered this behaviour a few years ago and one of his colleagues, Fiona Cross, has now found that the blood isn't just a meal for the spiders, it's an aphrodisiac too.

Photo of E.culicivora eating a mosquito, by R. Jackson.

Cross made spiders choose between two adults of the opposite sex, by wafting their smells down a tube on different days and seeing which drew the choosy spider's attention for the longest time. The contenders had been fed on one of four diets: blood-fed female mosquitoes, sugar-fed female mosquitoes, male mosquitoes, or lake flies.

Also at his blog, "a spider that must be an arachnophobe's worst nightmare."